The use of laser diodes to form a pumped light source for a solid state laser has been known for some time. The laser diodes are disposed on a module in a straight row, the module being disposed parallel to the longitudinal axis of the cylindrical laser rod spaced a small distance form the laser beam (IEEE Journal of Quantum Electronics, Vol 24, No. 6, June 1988, pages 895 to 911).
The use of laser diodes as a pumped light source is advantageous due to the relatively high power of the laser light (compared with light-emitting diodes), but it simultaneously raises certain problems with respect to the cooling.
A special feature of pumping laser diodes is that the radiated lobe of light is not rotationally symmetrical. The angle of dispersion parallel to the mounting surface is considerably smaller than perpendicular thereto. The beam does not diverge as quickly in the direction parallel to the mounting surface. Perpendicular to the mounting surface the angle of dispersion is very great. In the abovementioned known assembly this means that (unless an optical system is used) part of the light energy fails to be coupled into the laser rod and is thus lost.
It is known (U.S. Pat. No. 4,719,631) to cool pumping laser diode arrays by arranging a plurality of diodes of a pumping array disposed parallel to the longitudinal axis of the laser rod individually on respective ceramic cooling wafers, several such arrays being distributed about the laser rod. The aligned laser diodes thus form an array likewise extending in the longitudinal direction of the laser rod. The cooling measures are rather elaborate and expensive. The mechanical structure of such a solid state laser is extremely elaborate and expensive.
There is known from German published patent application No. DE-A 2,542,652 a solid state laser wherein the solid state medium is a hollow cylinder internally of which there is provided a rod-shaped diode array and externally of which it is surrounded by an additional tube-shaped diode array. By means of this arrangement there are defined between the solid state medium and the two diode arrays two annular hollow spaces for a cooling fluid. The diodes in both arrays are constructed as individual diodes, but as an alternative it is nonetheless possible to use fully integrated diode arrays in which the diodes can also be laser diodes. The indicated possible cooling by filling the annular spaces with a suitable cooling fluid makes it necessary to provide special sealing means, and over and above that the cooling fluid must have an appropriate refractive index.